Fluorinated sol-gel electro-optic materials, process for producing same, and devices therefrom

ABSTRACT

A process, comprising: a) reacting a an alkoxysilane, an (epoxy)alkoxysilane, and a fluorinated alkoxysilane to form a fluorinated sol-gel polymer; and b) reacting a nonlinear optical chromophore comprising a donor, a π-bridge, an acceptor, and at least one alkoxysilyl group with the fluorinated sol-gel polymer to form a nonlinear optical fluorinated sol-gel polymer.

STATEMENT OF RELATED CASES

This application is related to the following concurrently filed,commonly assigned patent applications, each of which is incorporated byreference: (a) Dinu et al., U.S. Ser. No. ______ entitled “PolymerSustained Microelectrodes;” (b) Dinu et al., U.S. Ser. No. ______entitled “Process of Fabricating Polymer Sustained Microelectrodes;” and(c) Dinu et al., U.S. Ser. No. ______ entitled “Process of FabricatingElectro-Optic Polymer Devices with Polymer Sustained Microelectrodes.”

BACKGROUND OF THE INVENTION

All patents, patent applications, and publications cited within thisapplication are incorporated herein by reference to the same extent asif each individual patent, patent application or publication wasspecifically and individually incorporated by reference.

Microelectrodes and microelectrode arrays are useful, for example, inmicroelectronics, semiconductor chips, integrated microanalysis chips(i.e., “labs on a chip”), electro-optics, and electro-chemical nucleicacid arrays. One conventional method of fabricating a microelectrode isto photolithographically pattern photoresist on a metal thin film, andthen wet etch areas of metal to leave the behind the electrode. Onedisadvantage to this approach is that certain critical dimensions suchas combinations of electrode spacing and thickness (height) may bedifficult to achieve because wet etching is an isotropic process.Another disadvantage is that the electrode walls after wet etching canbe relatively rough. Dry etching, which can be anisotropic and used toproduce less wall roughness, is difficult to achieve on the most usefulelectrode metals like gold.

The “lift-off” technique has been used as an alternative to wet etching.The lift-off technique involves patterning a photoresist on a surfacethen depositing a metal on the surface and the photoresist and thenstripping the gold covered photoresist to leave behind the metalelectrode. This technique usually requires a directional deposition ofthe metal since conformal coverage on the photoresist walls will notallow the stripper to dissolve the photoresist. Evaporation is typicallyused for directional deposition, but this is difficult to utilize inhigh volumes.

Physical vapor deposition (PVD) of metals, which is well proven in thesemi-conductor industry, is difficult to use in a lift-off process sincethe coverage in conformal. PVD can be used with a “two-layer”photoresist lift-off technique. In a two-layer process, the walls of thebottom layer of photoresist are recessed compared to the walls of theupper layer. The PVD conformal coverage occurs on the walls of the upperlayer of photoresist and the surface. A gap is left near the recessedwalls of the lower layer, thereby allowing the stripper to dissolve andremove the photoresist, leaving behind the metal electrode. Onedisadvantage to this approach is that the walls of the electrode can beslanted significantly.

SUMMARY OF THE INVENTION

One embodiment is a microelectrode comprising an upper surface, twowalls, and a polymer core, each of the two walls forming an angle with alower surface, wherein the upper surface and each of the two wallscomprise a metal thin film in contact with the polymer core, and thelower surface lacks a continuous metal thin film. The areas of the lowersurface that are not covered with metal provide electrical isolation forthe metal covering the upper surface and two walls, which allows themetal to be used as an electrode. The polymer core may comprise a linearpolymer, a crosslinked polymer, an organically modified sol-gel, or anycombination thereof. Another embodiment is a microelectrode comprising ametal thin film, the metal thin film having a thickness and a planebisecting the thickness, the plane forming an angle with a lowersurface, wherein: the metal thin film is in contact with a supportingpolymer, the supporting polymer having an upper surface; the lowersurface lacks a continuous metal thin film; and the upper surface lacksa continuous metal thin film. The lower surface and the upper surfacelack a continuous metal thin film. The supporting polymer may comprise alinear polymer, a crosslinked polymer, an organically modified sol-gel,or any combination thereof. Other embodiments include microelectrodearrays comprising the microelectrodes described herein.

Another embodiment is a process for fabricating a microelectrodecomprising: a) providing a substrate comprising at least one polymermicro-ridge, wherein the polymer micro-ridge comprises an upper surfaceand two walls, the two walls forming an angle with a lower surface; b)depositing a metal thin film on the upper surface, the two walls, andthe lower surface; and c) etching a predetermined amount of thedeposited metal thin film on the lower surface to form themicroelectrode. Etching a predetermined amount of the deposited metalthin film on the lower surface exposes a portion of the lower surface,thereby providing electrical isolation between the micro-ridge coveredwith metal and any other area of metal; the electrical isolation allowsthe metal-covered micro-ridge to be used as an electrode. Anotherembodiment is a process for fabricating a microelectrode that comprises:a) providing a substrate comprising at least one polymer micro-ridge,wherein the polymer micro-ridge comprises an upper surface and at leastone wall, the wall forming an angle with a lower surface; b) depositinga metal thin film on the upper surface, the wall, and the lower surface;c) etching a predetermined amount of the deposited metal thin film onthe lower surface or the deposited metal thin film on the upper surface;and d) etching a predetermined amount of the other of the depositedmetal thin film on upper surface or the deposited metal thin film on thelower surface, thereby leaving a metal thin film on the wall. In oneembodiment, the deposited metal thin film on the upper surface is etchedfirst, followed by the deposited metal thin film on the lower surface.Preferably, however, the deposited metal thin film on the lower surfaceis etched first, followed by deposited metal thin film on the uppersurface.

Another embodiment is a process for fabricating an electro-optic device,comprising: a) providing a substrate comprising at least two polymermicro-ridges, wherein each polymer micro-ridge comprises an uppersurface and two walls, the two walls forming an angle with a lowersurface; b) depositing a metal thin film on the upper surface, the twowalls, and the lower surface; c) etching a predetermined amount of thedeposited metal thin film on the lower surface, thereby forming twoelectrodes separated by a gap; d) depositing a nonlinear optical polymerin the gap between the two electrodes; and e) poling the nonlinearoptical polymer to induce electro-optic activity. Preferably, theprocess further comprises dry etching the electro-optic polymer so thatthe surface of the electro-optic polymer is substantially co-planar withthe upper surface of the polymer micro-ridge. In some embodiments, theprocess further includes etching the upper surface to remove apredetermined amount of metal thin film from the upper surface.

Another embodiment is a process comprising: a) reacting an alkoxysilane,an (epoxy)alkoxysilane, and a fluorinated alkoxysilane to form afluorinated sol-gel polymer; and b) reacting a nonlinear opticalchromophore comprising a donor, a n-bridge, an acceptor, and at leastone alkoxysilyl group with the fluorinated sol-gel polymer to form anonlinear optical fluorinated sol-gel polymer. The resulting nonlinearoptical sol-gel polymer can then be formed into structures that can bepoled to induce electro-optic activity. Another embodiment is acomposition made by the process described above. Such compositions maybe useful, for example, in fabrication electro-optic devices. Otherembodiments include electro-optic devices comprising the compositionmade by the process described above. The electro-optic devices mayinclude, for example, Mach-Zehnder modulators, directional couplers, andmicro-ring resonators.

Other features and advantages of the invention will be apparent from thefollowing description of preferred embodiments thereof, and from theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates in cross-sectional views some examples ofmicroelectrodes including a polymer core.

FIG. 2 illustrates in cross-sectional views some examples ofmicroelectrodes including forming an angle with a lower surface anddisposed on a supporting polymer.

FIGS. 3-6 illustrate in cross-sectional views some examples of processflows that may be used to fabricate the microelectrodes in FIGS. 1 and2.

FIGS. 7-9 illustrate in cross-sectional views some examples of processesfor fabricating an electro-optic device including the microelectrodes.

FIG. 10 illustrates some examples of nonlinear optical chromophorescontaining alkoxysilyl groups.

FIG. 11 is a scheme for preparing an example of a nonlinear opticalchromophore containing two alkoxysilyl groups.

FIG. 12 is a combined GPC trace of a fluorinated sol-gel polymer and afluorinated sol-gel polymer including a nonlinear optical chromophore.

DETAILED DESCRIPTION

Referring to FIG. 1 a, one embodiment is a microelectrode (2) comprisingan upper surface (4), two walls (6), and a polymer core (8), each of thetwo walls forming an angle with a lower surface (10), wherein the uppersurface and each of the two walls comprise a metal thin film (12) incontact with the polymer core, and the lower surface lacks a continuousmetal thin film. The areas of the lower surface that are not coveredwith metal (i.e., a metal thin film) provide electrical isolation forthe metal covering the upper surface and two walls, which allows themetal to be used as an electrode. However, small areas of the lowersurface may be covered with metal to form a “foot” (14, FIG. 1 b) ifelectrical isolation is maintained.

The polymer core may comprise a linear polymer, a crosslinked polymer,an organically modified sol-gel, or any combination thereof. The lowersurface preferably comprises silicon dioxide. In some embodiments, thelower surface comprises a polymer. When the lower surface is a polymer,the polymer can be a linear polymer, a crosslinked polymer, anorganically modified sol-gel, or any combination thereof. In someembodiments, the polymer core and the lower surface comprise the samepolymer.

Preferably, the upper surface and the lower surface are substantiallyparallel. In most embodiments, the angle between the two walls and thelower surface is about 90 degrees. The metal thin film can comprise anymetal or conductive metal alloy. Preferably, the thin film comprisesgold, platinum, titanium, or any combination thereof. In manyembodiments, the metal thin film has a thickness of about 100 nm toabout 5 μm. In some embodiments, the width of the upper surface is about2 μm to about 500 μm and the height of the two walls is about 200 nm toabout 10 μm. The length of the microelectrodes may be about 2 μm toabout 200 mm.

Another embodiment, referring to FIG. 2, is a microelectrode (16)comprising a metal thin film (12), the metal thin film having athickness and a plane (18) bisecting the thickness, the plane forming anangle with a lower surface (10), wherein: the metal thin film is incontact with a supporting polymer (20), the supporting polymer having anupper surface (22); the lower surface lacks a continuous metal thinfilm; and the upper surface lacks a continuous metal thin film. Theareas of the lower surface and the upper surface that are not coveredwith a metal thin film provide electrical isolation for the metal thinfilm in contact with the supporting polymer. However, the electrode mayhave a “foot” (14, FIG. 2 b) or an “overhang” (24, FIG. 2 b). Thesupporting polymer may comprise a linear polymer, a crosslinked polymer,an organically modified sol-gel, or any combination thereof The lowersurface may comprise silicon dioxide or a polymer. When the lowersurface comprises a polymer, preferably the polymer is a linear polymer,a crosslinked polymer, an organically modified sol-gel, or anycombination thereof. In some embodiments, the supporting polymer and thelower surface comprise the same polymer.

Preferably, the metal thin film is selected from the group consisting ofgold, platinum, titanium, and any combination thereof. The thickness ofthe metal thin film may be about 100 nm to about 5 μm. Preferably, theangle between the plane bisecting the thickness and the lower surface isabout 90 degrees. The width of the metal thin film, which is measuredfrom the lower surface to the upper surface of the supporting polymer,may be about 200 nm to about 10 μm. Preferably, length of themicroelectrode is about 2 μm to about 200 mm.

Other embodiments include a microelectrode array comprising more thanone of the microelectrodes described above and illustrated in FIGS. 1and 2. When there is more than one microelectrode, preferably, themicroelectrodes are interdigitated. The microelectrodes described aboveand microelectrode arrays including those microelectrodes can befabricated as described below.

Another embodiment is a process for making the electrode illustrated inFIG. 1. Thus, referring to FIG. 3, one embodiment is a process forfabricating a microelectrode comprising: a) providing a substrate (26)comprising at least one polymer micro-ridge (28), wherein the polymermicro-ridge comprises an upper surface (30) and two walls (32), the twowalls forming an angle with a lower surface (10); b) depositing a metalthin film (12) on the upper surface, the two walls, and the lowersurface; and c) etching a predetermined amount of the deposited metalthin film on the lower surface. Etching a predetermined amount of thedeposited metal thin film on the lower surface exposes a portion of thelower surface, thereby providing electrical isolation between themicro-ridge covered with metal and any other area of metal. The polymermicro-ridge functions as the polymer core (8) of the microelectrode (2).

Referring to FIG. 4, the etching may be accomplished, for example,by: 1) depositing a photoresist (34) on the deposited metal thin film;2) forming vias (36) through the photoresist by photolithographicpatterning and developing; and 3) etching a predetermined amount of thedeposited metal thin film to expose a portions of the lower surface (10)defined by the vias, and stripping the photoresist. Etching apredetermined amount of the deposited metal thin film, in turn, maycomprise techniques such as wet etching, dry etching, ion beambombardment, or any combination thereof.

Another embodiment is a process for fabricating the microelectrodeillustrated in FIG. 2. Thus, referring to FIG. 5, another embodiment isa process for fabrication a microelectrode that comprises: a) providinga substrate (26) comprising at least one polymer micro-ridge (28),wherein the polymer micro-ridge comprises an upper surface (30) and atleast one wall (32), the wall forming an angle with a lower surface(10); b) depositing a metal thin film (12) on the upper surface, thewall, and the lower surface; c) etching a predetermined amount of thedeposited metal thin film on the lower surface or the deposited metalthin film on the upper surface; and d) etching a predetermined amount ofthe other of the deposited metal thin film on upper surface or thedeposited metal thin film on the lower surface, thereby leaving a metalthin film on the wall. In one embodiment, the deposited metal thin filmon the upper surface is etched first, followed by the deposited metalthin film on the lower surface. Preferably, however, the deposited metalthin film on the lower surface is etched first, followed by depositedmetal thin film on the upper surface. FIG. 6 illustrates how, forexample, the deposited metal thin film on the lower surface may beetched first followed by the deposited metal thin film on the uppersurface: 1) depositing a photoresist (34) on the metal thin film; 2)forming a via (36) through the photoresist to the deposited metal thinfilm on the lower surface by photolithographic patterning anddeveloping; and 3) etching a predetermined amount the deposited metalthin film on the lower surface defined by the via (36), and strippingthe photoresist; 4) depositing photoresist again; 5) forming a via (36)through the photoresist to the deposited metal thin film on the uppersurface by photolithographic patterning and developing; 5) etching apredetermined amount the deposited metal thin film on the upper surfacedefined by the via (36), and stripping the photoresist. Etching apredetermined amount of deposited metal thin film on either the uppersurface or the lower surface, in turn, may comprise techniques such aswet etching, dry etching, ion beam bombardment, or any combinationthereof.

In the processes described above, the polymer micro-ridge provided canbe formed by methods comprising molding, imprinting, photolithographicpatterning, and imprint lithography. In one embodiment, providing asubstrate comprising at least one polymer micro-ridge comprises dryetching a polymer thin film. The polymer thin film may be provided bymethods including spin coating, dip coating, and brushing. Preferably,the polymer micro-ridge comprises a linear polymer, a crosslinkedpolymer, or an organically modified sol-gel.

In the processes described above, the lower surface may comprise silicondioxide. Alternatively, the lower surface may comprise a polymer. Whenthe lower surface comprises a polymer, preferably the polymer is alinear polymer, a crosslinked polymer, an organically modified sol-gel,or any combination thereof. In some embodiments, the polymer micro-ridgeand the lower surface are the same polymer.

Preferably, the angle between the two walls or at least one wall and thelower surface, is about 90 degrees. The upper surface and lower surfacemay be substantially parallel to each other. When the upper surface andlower surface are substantially parallel, preferably the wall/s aresubstantially perpendicular to the upper surface and the lower surface.

The substrate may comprise a plurality of polymer micro-ridges.Preferably, the micro-ridges are interdigitated, which means that themicroelectrodes are also interdigitated.

Any metal or conductive alloy can be deposited on the substrate if themetal can be etched in the following steps. Preferably, the metalcomprises gold, platinum, titanium, or any combination thereof. Themetal thin film may be deposited by methods including physical vapordeposition, thermal evaporation, electroplating, or any combinationthereof.

Another embodiment, referring to FIGS. 7 and 8, is a process forfabricating an electro-optic device, comprising: a) providing asubstrate (26) comprising at least two polymer micro-ridges (28),wherein each polymer micro-ridge comprises an upper surface (30) and twowalls (32), the two walls forming an angle with a lower surface (10); b)depositing a metal thin film (12) on the upper surface, the two walls,and the lower surface; c) etching a predetermined amount of thedeposited metal thin film on the lower surface, thereby forming twoelectrodes separated by a gap (36); d) depositing a nonlinear opticalpolymer (38) in the gap between the two electrodes; and e) poling thenonlinear optical polymer to induce electro-optic activity. Preferably,referring to FIG. 9, the process further comprises dry etching theelectro-optic polymer so that the surface (39) of the electro-opticpolymer is substantially co-planar with the upper surface of the polymermicro-ridge. In some embodiments, also referring to FIG. 9, the processfurther includes etching a predetermined amount of the deposited metalthin film on the upper surface of the polymer micro-ridge. Preferably,the gap (36) is about 2 μm to about 500 μm.

The polymer micro-ridge may comprise a linear polymer, a crosslinkedpolymer, an organically modified sol-gel, or any combination thereof.The width of the upper surface of the polymer micro-ridge may be about 2μm to about 500 μm and the height of the two walls may be about 200 nmto about 10 μm. Preferably, the angle between the two walls and thelower surface may be about 90 degrees. The upper surface and lowersurface may be substantially parallel.

The composition of the metal thin film and the deposition of the metalthin film may be as described above. Preferably, etching the depositedmetal thin film on the lower surface or the deposited metal thin film inthe upper surface comprises wet etching, dry etching, ion beambombardment, or any combination thereof. In some embodiments, the lowersurface comprises silicon dioxide or, preferably, the lower surfacecomprises a polymer. In some embodiments, the polymer micro-ridge andthe lower surface comprise the same polymer.

The nonlinear optical polymer may comprise a linear polymer, acrosslinkable polymer, an organically modified sol gel, or anycombination thereof. Preferably, the nonlinear optical polymer iscrosslinkable. When the nonlinear optical polymer is crosslinkable, theprocess may further comprise crosslinking the nonlinear optical polymer.The crosslinking may occur before poling, during poling, after poling,or any combination thereof. The crosslinking may occur by exposing thenonlinear optical polymer to heat, actinic radiation, or any combinationthereof. Depositing the nonlinear optical polymer may comprise spincoating, dip coating, or brushing. In most embodiments, the index ofrefraction of the nonlinear optical polymer is higher than the index ofrefraction of the lower surface.

The substrate may comprise more than two polymer micro-ridges. Thelength of the polymer micro-ridges may be about 2 μm to about 300 mm.Preferably, the polymer micro-ridges are interdigitated.

Another embodiment is a process comprising: a) reacting an alkoxysilane,an (epoxy)alkoxysilane, and a fluorinated alkoxysilane to form afluorinated sol-gel polymer; and b) reacting a nonlinear opticalchromophore comprising a donor, a π-bridge, an acceptor, and at leastone alkoxysilyl group with the fluorinated sol-gel polymer to form anonlinear optical fluorinated sol-gel polymer. The resulting nonlinearoptical sol-gel polymer can then be formed into structures that can bepoled to induce electro-optic activity. The nonlinear optical sol-gelpolymer can be heated to crosslink the material, which increases thestability of the electro-optic activity and the mechanical strength ofthe material. The alkoxy group of the alkoxysilane, the(epoxy)alkoxysilane, the (fluoroalkyl)alkoxysilane, or the alkoxysilylgroup of the nonlinear optical chromophore may, independently at eachoccurrence, be methoxy, ethoxy, propoxy, isopropoxy, butoxy, or anycombination thereof. Preferably, the alkoxysilane is atetraalkoxysilane. In some embodiments, the (epoxy)alkoxysilane mayfurther comprise one alkyl group or may comprise two epoxy groups.Preferably, the (epoxy)alkoxysilane comprises an epoxyalkyl group, anepoxycycloalkyl group, or any combination thereof. Some examples ofepoxyalkyl or epoxycycloalkyl groups are the 3-(2,3-epoxypropoxy)propylgroup, the 5,6-epoxyhexyl group, and the 2-(3,4-epoxycyclohexyl)ethylgroup. The fluorinated alkoxysilane may comprise a fluorinated groupincluding up to about 20 carbon atoms. The fluorinated groups remain inthe polymer after curing. Some examples of fluorinated groups includethe 3,3,3-trifluoropropyl group, the 3-heptafluoroisopropoxy)propylgroup, the pentafluorophenyl, pentafluoro-phenylpropyl group, theperfluoro-1,1,2,2-tetrahydrohexyl group, theperfluoro-1,1,2,2-tetrahydrooctyl group, theperfluoro-1,1,2,2-tetrahydrodecyl group, theperfluoro-1,1,2,2-tetrahydrododecyl group, and theperfluoro-1,1,2,2-tetrahydrododecyl group. The fluorinated alkoxysilanemay also comprise two fluoroalkyl groups. In other embodiments, thefluorinated alkoxysilane group may comprise a fluorocycloalkyl group.

Properties of the composition such as refractive index, electro-opticcoefficient, and glass transition temperature, as well as theprocessibility of the composition, can be changed by changing the ratioof the fluorinated alkoxysilane to the (epoxy)alkoxysilane and/or bychanging the loading weight percent of the nonlinear opticalchromophore. For example, increasing the amount of fluorinatealkoxysilane with respect to the (epoxy)alkoxysilane will tend todecrease the refractive index of the system if the amount of nonlinearoptical chromophore is held constant. Increasing the loading percent ofthe nonlinear optical chromophore will tend to increase the refractiveindex. Preferably, the molar ratio of the fluorinated alkoxysilane tothe (epoxy)alkoxysilane in the process described above is greater thanabout 0.1 to 4. Preferably, the weight percent of the nonlinear opticalchromophore in the fluorinated sol-gel polymer is about 10 weightpercent to about 50 weight percent. Preferably, reacting thetetraalkoxysilane, the (epoxy)alkoxysilane, and the fluorinatedalkoxysilane comprises catalysis with a catalyst comprisingdeuteriochloric acid (DCl) in deuterium oxide (D₂O).

Preferably, the process further comprises c) forming a thin filmcomprising the nonlinear optical fluorinated sol-gel on a substrate; andd) poling the nonlinear optical fluorinated sol-gel to form anelectro-optic fluorinated sol-gel. Forming the thin film may comprisespin coating, dip coating, or brushing. The substrate may furthercomprise a cladding material that has an index of refraction lower thanthe index of refraction of the electro-optic fluorinated sol-gel.Preferably, the cladding material comprises a polymer.

The alkoxysilyl group of the nonlinear optical chromophore is preferablya trialkoxysilyl group. Referring to FIG. 10, the alkoxysilyl group ofthe nonlinear optical chromophore may be attached to the donor (forexample 40) or to the acceptor (for example 42). In some embodiments,the nonlinear optical chromophore comprises two alkoxysilyl groups.Preferably, the two alkoxysilyl groups are attached to the donor (forexample 44). In some embodiments, one alkoxysilyl group is attached tothe donor and one alkoxysilyl group is attached to the acceptor (forexample 46). Alkoxysilyl groups may be attached chromophores by reactionof a reactive functional group of one the alkoxysilyl group orchromophore with a complimentary reactive functional group on the otherof the alkoxysilyl group or chromophore. Some examples of reactivefunctional groups/complimentary reactive functional groups areisocyanates/alcohols, isocyanates/amines, acid chlorides/alcohols, andacid chlorides/amines. FIG. 11 illustrates a scheme of an example wherealcohols on the chromophore (48) are reacted with an isocyanate of thealkoxysilyl group.

Preferably, the π-bridge of the nonlinear optical chromophore comprisesa thiophene ring having oxygen atoms bonded directly to the 3 and 4positions of the thiophene ring, for example

wherein R is an alkyl group, a heteroalkyl group, an aryl group, or aheteroaryl group.

Another embodiment is a composition made by the process described above.Such compositions may be useful, for example, in fabricationelectro-optic devices. Other embodiments include electro-optic devicescomprising the composition made by the process described above. Theelectro-optic devices may include, for example, Mach-Zehnder modulators,directional couplers, and micro-ring resonators.

EXAMPLES

The following example(s) is illustrative and does not limit the Claims.

The following example describes the preparation of microelectrodes thatinclude polymer micro-ridges, where the gap between the microelectrodeswas about 14 μm.

A 6 inch Si/SiOx (1 μm) wafer or quartz wafer was cleaned in aqueousH₂O₂/NH₄OH at 70° C. for 10 minutes, dump-rinsed with 18 megaohm water 6times, and spin-rinse dried. The wafer was then further cleaned withoxygen plasma for 7 minutes. An adhesion promoter (1% by weight ofpoly(N-(2-aminoethyl)-3-aminopropylmethyl-dimethoxysilane) in isopropylalcohol was filtered through a 0.1 μm Teflon filter and spin depositedon the wafer at 500 rpm for 3 sec and 3000 rpm for 30 sec. The wafer wasthen heated on a nitrogen-flushed hotplate for 7 min at 100° C.

A UV curable acrylate resin 45% by weight in solvent was filteredthrough 0.1 mm Nylon filter and spin deposited on the wafer at 500 rpmfor 3 sec and 1000 rpm for 30 sec. The resin was baked at 50° C. for 60min in a vacuum oven. The wafer was passed under a UV lamp on a conveyorbelt until the resin was cured to hardness. The resulting layer of UVcrosslinked polymer was 3.4 μm thick. A second layer of UV crosslinkedpolymer was then deposited on the first layer to give a UV crosslinkedpolymer film with a thickness of about 7 μm.

A thin film of titanium used to form a dry etching hardmask wasdeposited on the UV crosslinked polymer thin film as described inco-pending, commonly assigned U.S. application Ser. No. 10/264,461. Theband-shaped polymer micro-ridges were dry etched by: 1) dry etching thetitanium thin film with 12.5 sccm SF₆/10 sccm Ne at 20 mTorr and 170Vreactive ion etching (RIE) for 4 min) to form the hardmask; 2) dryetching the UV crosslinked polymer with 100 sccm O₂ at 6 mTorr and 240 Vfor 15 min, breaking for 10 min, and then repeating the 15 min O₂etch/10 min break cycle eleven times; and 3) dry etching the titaniumhardmask with 12.5 sccm SF₆/10 sccm Ne at 20 mTorr and 170V RIE for 4min.

The wafer was then flood exposed to UV light for 100 sec, immersed inMF24A developer from Cyantek for 5 min, and sprayed with MF24Adeveloper. The wafer was dump-rinsed with 18 megaohm water twelve times,spin-rinse dried, and cleaned with 100 sccm of O₂ at 20 mTorr and 220Vfor 3 min. This provided the substrate comprising polymer micro-ridges.

An adhesion layer of titanium was deposited on the substrate bypresputtering for 360 sec and sputtering for 100 sec. After 30 min, alayer of platinum was deposited by presputtering for 360 sec andsputtering for 80 sec. After a 30 sec vent, gold was deposited on thesubstrate by presputtering for 360 sec and sputtering for a total of 44min. The gold sputtering was broken down into cycles of about 30 secvent times followed by 100 sec of sputtering.

A 4.5 μm thick layer of SPR220-45 photoresist from Shipley was spindeposited on the wafer and soft baked in the vacuum oven for 16 h at10⁻³ Torr. The clear field of the photolithographic mask was alignedover the lower surface. The photoresist was exposed for 20 sec at 32mW/cm². The pattern was developed to provide via to the lower surface.The gold was wet etched with aqueous potassium iodide/iodine wet etchantfor 2 min. The remaining photoresist was stripped with RS 112 fromCyantek for 2 min. The wafer was then immersed in a bath of isopropylalcohol for 1 min, immersed in a second bath of isopropyl alcohol for anadditional 1 min, dump-rinsed with 18 megaohm water twelve times, andthen spin-rinse dried. The titanium and platinum adhesion layer wasremoved from the lower surface by dry etching with 12.5 sccm of SF₆/90sccm Ne at 20 mTorr with 300W inductively coupled plasma (ICP)/170V RIEfor 5 min followed by waiting for 10 min. The dry etch/wait process wasrepeated seven times.

Inducing electro-optic activity in a nonlinear optical polymer was usedto demonstrate the performance of the electrodes fabricated above. Afluorinated nonlinear optical sol-gel polymer (described below) was spincoated on the wafer at 400 rpm for 40 sec and 600 rpm for 30 sec. Thewafer was baked at 100° C. for 10 min and 190° C. for 1.5 h on anitrogen-flushed hot plate. Areas of polymer were physically removed tomake electrical contact with the electrodes. At room temperature, 850 Vwas applied to the sample and the sample was heated to 140° C. andmaintained at 140° C. for 500 sec. The sample was then heated to about180° C. over 1000 sec and then cooled to room temperature over 1500 sec.A laser beam was focused on the sample and a second harmonic generation(SHG) signal demonstrated that the voltage applied induced electro-opticactivity in the nonlinear optical polymer between the electrodes.

The following example describes the preparation of a fluorinatednonlinear optical sol-gel.

Preparation of the Chromophore:

Referring to FIG. 11, a trialkoxysilyl-functionalized chromophore wasprepared from chromophore 48. Chromophore 48 can be prepared asdescribed in copending, commonly assigned U.S. application Ser. No.10/301,978. A solution of 12 g (0.0134 mol) of 48, 13.3 g (0.0536 mol)of freshly distilled 3-(triethoxysilyl)propyl isocyanate, and acatalytic amount of dibutyltin dilaurate (5 drops) were dissolved in atotal of 300 mL of dry THF and the resulting solution was refluxed for 4hours. The reaction was allowed to cool to room temperature and the THFwas removed under reduced pressure. The crude material was purified byflash column chromatography (eluent=hexanes/CH₂Cl₂/ethyl acetate, 2:4:2)to give 12 g (64%) of the trialkoxysilyl-functionalized chromophore 44as a dark blue solid.

Preparation of a fluorinated sol-gel:

A fluorinated sol-gel was prepared by adding 99.96 g (0.48 mol) oftetraethoxysilane, 236.3 g (0.12 mol) of3-glycidoxypropyltrimethoxysilane, 122.40 g (0.24 mol) oftridecafluorotetrahydrooctyltriethoxysilane, and 312 g of isopropylalcohol to a 1 L round bottom flask. The resulting mixture was stirredand a solution of 4.32 g of 2M DCI in 60 g of D₂O was added dropwiseslowly until the mixture became clear. The resulting solution wasrefluxed for 3 h then allowed to cool to room temperature overnight. Theisopropyl alcohol and other volatile reaction products were removedunder reduced pressure. The resulting solution was diluted with 200 g ofn-butanol, 40 g of cyclopentanone, and stored in 0° C. refrigerator.

Preparation of a fluorinated nonlinear optical sol-gel:

A fluorinated nonlinear optical sol-gel was prepared by dissolving 1.74g of 44 in 10 g of distilled cyclopentanone. The resulting solution wasadded dropwise slowly with stirring to 24.858 g of the fluorinatedsol-gel solution prepared above (solid concentration was 33.15 wt %). Tothe resulting solution was added 0.0698 g of distilled water and thereaction was immersed in a 70° C. bath with magnetic stirring.Typically, the reaction lasts two to three days to incorporate about 17%by weight of the chromophore with respect to the fluorinated sol-gel.The incorporation of the chromophore was evidenced with GPC usingrefractive index detection. The GPC trace of the fluorinated sol-gelwith THF as the solvent gave a “negative peak” 60 (FIG. 12) because therefractive index of the fluorinated sol-gel was lower than therefractive index of THF. The GPC trace of the fluorinated nonlinearoptical sol-gel with THF gave a “positive peak” 62 (FIG. 12) becauseincorporation of the chromophore raised the refractive index of thefluorinated nonlinear optical sol-gel higher than the refractive indexof THF. The volatiles from the above reaction were removed under reducedpressure to give a solution that could be deposited to form a thin film.

The fluorinated nonlinear optical sol-gel prepared above was spindeposited on a 2″ ITO covered glass wafer to give a 5.9 μm thick film.The film was cured at 190° C. for 30 minutes to give a refractive indexof 1.446±0.002 at 1.5 μm. The same solution was spin coated on an ITOcoated glass substrate and cured at 180° C. for about 100 sec, followedby cooling to 50° C. over about 100 sec. The film was corona poled byapplying about 3.75 V through a needle and heating the sample to 190° C.over about 200 sec. The film was poled at 190° C. for about 300 sec thenthe applied voltage was increased to about 8 kV. After about 100 sec,the film was cooled to about 100° C. over about 100 sec and then heatedagain to 190° C. over about 200 sec. The film was poled at 190° C. for afurther 150 sec at 8 kV, then cooled to room temperature over about 300sec. The r₃₃ at 1.3 μm determined by the Teng-Man method was 36 pm/V.

Other embodiments are within the following claims.

1. A process, comprising: a) reacting a an alkoxysilane, an(epoxy)alkoxysilane, and a fluorinated alkoxysilane to form afluorinated sol-gel polymer; and b) reacting a nonlinear opticalchromophore comprising a donor, a π-bridge, an acceptor, and at leastone alkoxysilyl group with the fluorinated sol-gel polymer to form anonlinear optical fluorinated sol-gel polymer.
 2. The process of claim1, wherein the alkoxy group of one or more of the alkoxysilane, the(epoxy)alkoxysilane, the (fluoroalkyl)alkoxysilane, or the alkoxysilylgroup of the nonlinear optical chromophore is independently selectedfrom the group consisting of methoxy, ethoxy, propoxy, isopropoxy,butoxy, and any combination thereof.
 3. The process of claim 1, whereinthe alkoxysilane is a tetraalkoxysilane.
 4. The process of claim 1,wherein the (epoxy)alkoxysilane further comprises one alkyl group. 5.The process of claim 1, wherein the (epoxy)alkoxysilane comprises twoepoxy groups.
 6. The process of claim 1, wherein the (epoxy)alkoxysilanecomprises an epoxyalkyl group, a epoxycycloalkyl group, or anycombination thereof.
 7. The process of claim 6, wherein the(epoxy)alkoxysilane comprises a 3-(2,3-epoxypropoxy)propyl group, a5,6-epoxyhexyl group, a 2-(3,4-epoxycyclohexyl)ethyl group, or anycombination thereof.
 8. The process of claim 1, wherein the fluorinatedalkoxysilane comprises a fluorinated group including up to about 20carbon atoms.
 9. The process of claim 8, wherein the fluorinated groupis selected from the group consisting of a 3,3,3-trifluoropropyl group,a 3-(heptafluoroisopropoxy)propyl group, a pentafluorophenyl,pentafluoro-phenylpropyl group, a perfluoro-1,1,2,2-tetrahydrohexylgroup, a perfluoro-1,1,2,2-tetrahydrooctyl group, aperfluoro-1,1,2,2-tetrahydrodecyl group, aperfluoro-1,1,2,2-tetrahydrododecyl group, aperfluoro-1,1,2,2-tetrahydrododecyl group, and any combination thereof.10. The process of claim 1, wherein the fluorinated alkoxysilanecomprises two fluoroalkyl groups.
 11. The process of claim 1, whereinthe fluorinated alkoxysilane comprises a fluorocycloalkyl group.
 12. Theprocess of claim 1, wherein the molar ratio of the fluorinatedalkoxysilane to the (epoxy)alkoxysilane is greater than about 0.1 to 4.13. The process of claim 1, wherein the weight percent of the nonlinearoptical chromophore in the fluorinated sol-gel polymer is about 10weight percent to about 50 weight percent.
 14. The process of claim 1,comprising catalyzing the reaction of the tetraalkoxysilane, the(epoxy)alkoxysilane, and the fluorinated alkoxysilane with a catalystcomprising deuteriochloric acid in deuterium oxide.
 15. The process ofclaim 1, further comprising c) forming a thin film comprising thenonlinear optical fluorinated sol-gel on a substrate; and d) poling thenonlinear optical fluorinated sol-gel to form an electro-opticfluorinated sol-gel.
 16. The process of claim 15, wherein forming thethin film comprises spin coating, dip coating, or brushing.
 17. Theprocess of claim 15, wherein the substrate further comprises a claddingmaterial, the cladding material having an index of refraction lower thanthe index of refraction of the electro-optic fluorinated sol-gel. 18.The process of claim 17, wherein the cladding material comprises apolymer.
 19. The process of claim 1, wherein the alkoxysilyl group ofthe nonlinear optical chromophore comprises a trialkoxysilyl group. 20.The process of claim 1, wherein the alkoxysilyl group of the nonlinearoptical chromophore is attached to the donor.
 21. The process of claim 1wherein the alkoxysilyl group of the nonlinear optical chromophore isattached to the acceptor.
 22. The process of claim 1, wherein thenonlinear optical chromophore comprises two alkoxysilyl groups.
 23. Theprocess of claim 22, wherein the two alkoxysilyl groups are attached tothe donor.
 24. The process of claim 23, wherein one alkoxysilyl group isattached to the donor and one alkoxysilyl group is attached to theacceptor.
 25. The process of claim 1, wherein the π-bridge comprises athiophene ring having oxygen atoms bonded directly to the 3 and 4positions of the thiophene ring.
 26. The process of claim 25, whereinthe π-bridge has the structure

wherein R is an alkyl group, a heteroalkyl group, an aryl group, or aheteroaryl group.
 27. A composition prepared according to the process ofclaim 1 or
 15. 28. An electro-optic device comprising the composition ofclaim
 27. 29. The electro-optic device of claim 28, including aMach-Zehnder modulator, a directional coupler, or a micro-ringresonator.